Nitrate is the best/fastest form of nitrogen for cannabis but is also the most expensive and easy to leach therefore not very efficient outdoor,ammoniacal is readily available but is the worst for the plant and the easiest to overdose,urea is useful in soil only and for big operations because is cheap and needs to be broken down by bacteria.Fusarium isn't a big problem,if your soil(and the plant) is healthy it should not attack as is easily outcompeted by beneficials bacteria/fungi.In hydro nitrate is the way to go.